1. Technical Field
The present invention relates to a method for manufacturing metal nanoparticles and more particularly, to a method for manufacturing metal nanoparticles which provides uniform particle size and allows mass production.
2. Description of the Related Art
There is a large demand for metal patterning of a thin film and forming a fine wiring on a substrate through the inkjet method in response to trends for electronic devices with greater densifications and smaller sizes. To this end, it is necessary to develop conductive ink made of metal nanoparticles having uniform shape, a narrow particle distribution, and excellent dispersibility.
There are various methods for manufacturing metal nanoparticles such as mechanical grinding method, co-precipitation method, spray, sol-gel method, electro-deposition method, and microemulsion method, etc. A problem associated with the co-precipitation method is that the method may difficult to control particle size, shape and particle distribution and problems associated with the sol-gel method are high production costs and difficulties in mass production. On the other hand, the microemulsion method provides easy control of particle size, shape and particle distribution but the process is complicate and thus not suitable for practical uses.
A conventional method for manufacturing nanoparticles in a solution has a limitation of concentration. That is, only a concentration of less than 0.01 M is used to produce nanoparticles having uniform size and even its production yield is very low. Thus, at least 1000 liter of a reactor is required to produce gram(g) volumes of nanoparticles having uniform size.
Silver nanoparticles have been produced by using thiol or fatty acid compound. The thiol compound has a strong bond with novel metals such as gold and silver and is able to control the particle size. The fatty acid compound is also able to control the particle size even though the bond with novel metals is less that the thiol compound. However, the amine compound has a weak bond with silver, so that it is difficult to produce stable silver nanoparticles.
Recently, a method for manufacturing gold or silver nanoparticles using silver acetate, oleylamine, and an organic solvent has been introduced. However, a reaction time is more than 8 hours and a yield is about 10% which is very low. In this method, phenylhydrazine can be used as a reducing agent to produce silver nanoparticles but it is a carcinogenic compound and thus not applicable for industrial production. Further, silver acetate is very costly and thus not suitable for mass production. Accordingly, such conventional methods are not suitable for mass production of metal nanoparticles having high dispersion stability in high yield.